The present invention relates to a traffic divider, and in particular to a bifilar (i.e. forming two rows) asymmetric barrier, with an amount of earth interposed for the purpose of providing an ornamental hedge acting as protection means against light rays.
More specifically, the barrier according to the invention is a barrier of this kind, having a New Jersey profile comprising several prefabricated modules.
As known, road safety barriers, and in particular those to be installed as traffic dividers on motorways, are required to withstand high energies of about 600 kJ, in order to prevent being dislodged by vehicles having a weight of more than 40 tons and a high centre of gravity.
Barriers with a high resistance are therefore very rigid; for this reason, upon impact by a light vehicle (automobiles having a weight between 800 and 1500 Kg), even at very high speeds corresponding to energies up to 70 kJ, no problem is encountered with respect to vehicle retention, but the decelerations transmitted to the passengers may be very high and fatal.
In many cases of accidents caused by automobiles, the relatively low energies involved, are not sufficient to trigger a displacement of the barrier so as to calibrate and reduce the decelerations.
Barriers preventing dislodging by vehicles with a weight between 3 and 44 tons, may represent a fatal obstacle (because of their rigidity) upon impact by automobiles having a weight comprised between 800 and 1500 Kg.
On the other hand, it is obvious, however, that in the field of safety barriers for roads the most important problem is to obtain protection and prevent displacement of the barrierxe2x80x94particularly in the case of traffic dividersxe2x80x94, for the whole variety of vehicles circulating on the road, which have extremely different masses, dimensions and velocities.
At present, the bivalence or twofold nature of the barrier (the guarantee of protection both for heavy vehicles and light vehicles), is obtained using barriers made of concrete and with a shape of their inner sidexe2x80x94facing the roadxe2x80x94, which is named xe2x80x9cNew Jerseyxe2x80x9d, and which is useful for xe2x80x9cliftingxe2x80x9d the light vehicle and realign it with respect to the carriageway, in case of very low impact energies.
The impact energy is low if the impact angle and/or the velocity is low.
Summing up, the present xe2x80x9cNew Jerseyxe2x80x9d barriers used as traffic dividers, having an amount of interposed earth, are unable to calibrate the decelerations which the barrier transmits to a light vehicle hitting the barrier with a high impact angle and a high velocity; the impact energy of the light vehicle, being high but not extremely high, may fail to cause a displacement of the barrier, which has a considerable mass (about 3 tons per meter).
Actually, the vehicle path is redirected but the the passengers may be severely injured or die, due to the high accelerations transmitted during the impact.
An object of the present invention is to realize a traffic divider of the New Jersey type made of prefabricated concrete modules, being suited to calibrate the decelerations of the vehicle upon impact, according to the type of vehicle and its impact energy, the latter being determined by its mass, velocity and impact angle with respect to the barrier.
The barrier of the present invention must however always ensure the retention of a colliding vehicle having a noticeable mass (from 3 to 44 tons), so as to maintain its xe2x80x9cbivalencexe2x80x9d.
Moreover, the barrier must ensure, by means of the earth interposed between the two rows of the New Jersey barrier, the realization and maintenance of an ornamental hedge serving as a means of protection against light rays.
The above object is obtained with a two-row (bifilar) asymmetric barrier, comprising a mass of interposed earth, by providing a receptacle for said earth, which is laid on the embankment and forms two continuous gaps (spaces) behind the rear wall of each element of the barrier.
Preferably, said receptacle is formed by a xe2x80x9csackxe2x80x9d of nonwoven fabric, suited to allow the passage of rain water and to ensure the growth and maintenance of the hedge.
The receptacle is preferably laid on the embankment, between both elements of the traffic divider, and is hooked to brackets or supports fixed at the upper ends of the barrier elements.
In this manner, the calibration of the resistant forces (and of the resultant decelerations) in case of impacts caused by automobiles with energies up to 65-70 kJ, is obtained through a first xe2x80x9cfreexe2x80x9d displacement, of some centimeters, and through a second step which starts when the barrier which is hit by the vehicle abuts the mass of earth (loam soil which is lightened by the addition of expanded clay or the like) contained inside the sack, and causes a partial lateral compression of said earth, since the latter is neither much compacted, nor hindered by an obstacle on its rear side.
Therefore, since the mass of earth (before impact and in the initial condition) does not abut the barrier elements, the barrier is able to move rearwards , thereby limiting the vehicle deceleration.
On the other hand, in case of an impact caused by a heavy vehicle, where the energies involved are much higher, the displacement of the barrier does not end after the step previously described, instead, it continues and causes the displacement of the sack, until abutment with the other barrier element and compression of said amount of earth occurs.
The barrier is therefore suited to provide resistant forces which increase as a function of the energies involved during the impact, and at the same time it is suited to calibrate the decelerations of the vehicle and consequently of its passengers.
In order to facilitate the displacement of the barrier, during the first step of the impact, or in case of an impact due to a light vehicle, according to a further aspect of the invention the barrier may be provided on its lower side with devices or runners which are fixed to the module of the barrier and/or to the support of the foundation (for instance the curbstone made of concrete, the road pavement or the soil).
Varying the relevant parameters such as the weight of the barrier, the extension of the runner""s surface, the features of the abutting surfaces (friction coefficient), it is possible to improve calibration of the decelerations in the first step of the impact.
Preferably, the runners are formed by stainless steel plates with a flat smoothed surface.
It is possible to fix a first stainless steel plate to a barrier module, and a second steel plate of identical extension, to the foundation curbstone, if any, or to the pavement.
Between said plates it is possible to insert a sheet or layer of material with a low friction coefficient, like xe2x80x9cTeflon,xe2x80x9d for instance.